Chondrus crispus Stackhouse

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Common names: Irish Moss, Carragheen, Carrageen, Carrageen Moss (Eng.), Mousse d'Irlande (French), Irisch Moos (German), Carraigín (Irish)
Description: Cartilaginous, dark purplish-red fronds, female plants sometimes iridescent at the apices under water (bottom right) when in good condition  and turning almost completely greenish-yellow in upper-shore rock-pools;  to 150 mm high. Stipe compressed, narrow, expanding gradually onto a flat, repeatedly dichotomously branched blade, in tufts from a discoid holdfast. Axils rounded, apices blunt or subacute, frond thicker in centre than margins. Very variable in breadth of segments.
Habitat: On rocks (above), in pools, lower intertidal and shallow subtidal, widely distributed, abundant.
Variability:  This is one of the most varibale species in the North Atlantic in size, colour, branching, broadness of fronds; at one time it was known as Fucus polymorphus. 
Usage: A source of carrageenan (a sulphated polysaccharide), and used to make soups, jellies, etc., and in Ireland as a remedy for respiratory disorders (colds, influenza and tuberculosis). The colloquial English name "Carrageen" was introduced in Ireland about 1840 by a Mr Todhunter from Donegal and is likely to have been taken from Carrigeen (or Carrigan) Head in Co. Donegal and not from a town or townland name in Co. Waterford; however, Carrageen or Carrigeen (carraigín, Irish: literally "little rock") is an ver common placename in Ireland. Chondrus crispus plants gathered in the shallow subtidal of some of the Maritime Provinces of Canada is an important source of the industrially-important hydrocolloid carrageenan. Irish Moss has been used in Ireland since the beginning of the 19th century as a folk remedy for respiratory ailments. Its use was exported to New England in the USA by famine emigrees in the mid-19th century and was expanded to include sizing of ropes and cooking. Small amounts are still collected in Ireland for cooking and as a health drink. In Canada, Acadian Seaplants grow colour and morphological variants of this species, which is sold dried as a novelty salad (Hana Tsunomata®).
Similar species: In Ireland,  Mastocarpus stellatus is frequently collected with Chondrus crispus and sold as a mixture under the name Carrageen or Irish Moss.
Note: in Germany there is currently a line of personal toiletries known as Irisch Moos.
Link: AlgaeBase
Photographs © M.D. Guiry

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